Thread: Exhaust and Inlet manifold

Series 2/3 Landrovers have the two manifolds bolted to each other, as you surmise, to provide a hot spot in the intake manifold. This was very common in carburetor engined vehicles, and most that did not use it had something to replace it, such as in the earlier Series 1 engine with manifolds on opposite sides, that had the inlet manifold heated by a coolant jacket.

Basically the idea is to make up for some of the shortcomings of the carburetor - namely that latent heat of vaporisation cools the mixture coming from the carburetor, often to the extent of precipitating out some of the petrol, especially at low throttle openings and in cool weather, leading to pools of fuel accumulating in the manifold - and leading to unplanned mixture changes when the throttle is opened increasing airflow and reducing manifold vacuum. This can cause severe driveability issues, especially in cold weather.

In the case of your Series 3, if fitting extractors, and hence losing the hotspot, the only noticeable effect is likely to be that it becomes (more) temperamental with the engine cold, especially in cold weather, but probably not a serious issue for most places in Australia.